From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: Quan Xu <quan.xu03@gmail.com>
Cc: kvm@vger.kernel.org, linux-doc@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org, x86@kernel.org,
xen-devel@lists.xenproject.org,
Yang Zhang <yang.zhang.wz@gmail.com>
Subject: Re: [Xen-devel] [PATCH RFC v3 0/6] x86/idle: add halt poll support
Date: Wed, 15 Nov 2017 16:31:31 -0500 [thread overview]
Message-ID: <20171115213131.GB21113@char.us.oracle.com> (raw)
In-Reply-To: <1510567565-5118-1-git-send-email-quan.xu0@gmail.com>
On Mon, Nov 13, 2017 at 06:05:59PM +0800, Quan Xu wrote:
> From: Yang Zhang <yang.zhang.wz@gmail.com>
>
> Some latency-intensive workload have seen obviously performance
> drop when running inside VM. The main reason is that the overhead
> is amplified when running inside VM. The most cost I have seen is
> inside idle path.
Meaning an VMEXIT b/c it is an 'halt' operation ? And then going
back in guest (VMRESUME) takes time. And hence your latency gets
all whacked b/c of this?
So if I understand - you want to use your _full_ timeslice (of the guest)
without ever (or as much as possible) to go in the hypervisor?
Which means in effect you don't care about power-saving or CPUfreq
savings, you just want to eat the full CPU for snack?
>
> This patch introduces a new mechanism to poll for a while before
> entering idle state. If schedule is needed during poll, then we
> don't need to goes through the heavy overhead path.
Schedule of what? The guest or the host?
WARNING: multiple messages have this Message-ID (diff)
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: Quan Xu <quan.xu03@gmail.com>
Cc: Yang Zhang <yang.zhang.wz@gmail.com>,
kvm@vger.kernel.org, linux-doc@vger.kernel.org, x86@kernel.org,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org,
linux-fsdevel@vger.kernel.org, xen-devel@lists.xenproject.org
Subject: Re: [Xen-devel] [PATCH RFC v3 0/6] x86/idle: add halt poll support
Date: Wed, 15 Nov 2017 16:31:31 -0500 [thread overview]
Message-ID: <20171115213131.GB21113@char.us.oracle.com> (raw)
In-Reply-To: <1510567565-5118-1-git-send-email-quan.xu0@gmail.com>
On Mon, Nov 13, 2017 at 06:05:59PM +0800, Quan Xu wrote:
> From: Yang Zhang <yang.zhang.wz@gmail.com>
>
> Some latency-intensive workload have seen obviously performance
> drop when running inside VM. The main reason is that the overhead
> is amplified when running inside VM. The most cost I have seen is
> inside idle path.
Meaning an VMEXIT b/c it is an 'halt' operation ? And then going
back in guest (VMRESUME) takes time. And hence your latency gets
all whacked b/c of this?
So if I understand - you want to use your _full_ timeslice (of the guest)
without ever (or as much as possible) to go in the hypervisor?
Which means in effect you don't care about power-saving or CPUfreq
savings, you just want to eat the full CPU for snack?
>
> This patch introduces a new mechanism to poll for a while before
> entering idle state. If schedule is needed during poll, then we
> don't need to goes through the heavy overhead path.
Schedule of what? The guest or the host?
next prev parent reply other threads:[~2017-11-15 21:31 UTC|newest]
Thread overview: 99+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-13 10:05 [PATCH RFC v3 0/6] x86/idle: add halt poll support Quan Xu
2017-11-13 10:06 ` [PATCH RFC v3 1/6] x86/paravirt: Add pv_idle_ops to paravirt ops Quan Xu
2017-11-13 10:53 ` Juergen Gross
2017-11-13 11:09 ` Wanpeng Li
2017-11-13 11:09 ` Wanpeng Li
2017-11-13 11:09 ` Wanpeng Li
2017-11-13 11:09 ` Wanpeng Li
2017-11-14 7:02 ` Quan Xu
2017-11-14 7:02 ` Quan Xu
2017-11-14 7:02 ` Quan Xu
2017-11-14 7:12 ` Wanpeng Li
2017-11-14 7:12 ` Wanpeng Li
2017-11-14 8:15 ` Quan Xu
2017-11-14 8:15 ` Quan Xu
2017-11-14 8:15 ` Quan Xu
2017-11-14 8:22 ` Wanpeng Li
2017-11-14 8:22 ` Wanpeng Li
2017-11-14 8:22 ` Wanpeng Li
2017-11-14 8:22 ` Wanpeng Li
2017-11-14 10:23 ` Quan Xu
2017-11-14 10:23 ` Quan Xu
2017-11-14 10:23 ` Quan Xu
2017-11-14 10:23 ` Quan Xu
2017-11-14 8:22 ` Wanpeng Li
2017-11-14 8:15 ` Quan Xu
2017-11-14 7:12 ` Wanpeng Li
2017-11-14 7:12 ` Wanpeng Li
2017-11-14 7:30 ` Juergen Gross
2017-11-14 7:30 ` Juergen Gross
2017-11-14 9:38 ` Quan Xu
2017-11-14 10:27 ` Juergen Gross
2017-11-14 11:43 ` Quan Xu
2017-11-14 11:43 ` Quan Xu
2017-11-14 11:43 ` Quan Xu
2017-11-14 11:58 ` Juergen Gross
2017-11-14 11:58 ` Juergen Gross
2017-11-14 11:58 ` Juergen Gross
2017-11-14 10:27 ` Juergen Gross
2017-11-14 10:27 ` Juergen Gross
2017-11-14 9:38 ` Quan Xu
2017-11-14 9:38 ` Quan Xu
2017-11-14 7:30 ` Juergen Gross
2017-11-13 10:53 ` Juergen Gross
2017-11-13 10:53 ` Juergen Gross
2017-11-13 10:06 ` Quan Xu
2017-11-13 10:06 ` [PATCH RFC v3 2/6] KVM guest: register kvm_idle_poll for pv_idle_ops Quan Xu
2017-11-13 10:06 ` Quan Xu
2017-11-13 10:06 ` [PATCH RFC v3 3/6] sched/idle: Add a generic poll before enter real idle path Quan Xu
2017-11-15 12:11 ` Peter Zijlstra
2017-11-15 12:11 ` Peter Zijlstra
2017-11-15 22:03 ` Thomas Gleixner
2017-11-15 22:03 ` Thomas Gleixner
2017-11-15 22:03 ` Thomas Gleixner
2017-11-16 8:45 ` Peter Zijlstra
2017-11-16 8:45 ` Peter Zijlstra
2017-11-16 8:58 ` Thomas Gleixner
2017-11-16 8:58 ` Thomas Gleixner
2017-11-16 8:58 ` Thomas Gleixner
2017-11-16 9:29 ` Quan Xu
2017-11-16 9:29 ` Quan Xu
2017-11-16 9:47 ` Thomas Gleixner
2017-11-16 9:47 ` Thomas Gleixner
2017-11-16 9:47 ` Thomas Gleixner
2017-11-16 9:29 ` Quan Xu
2017-11-16 8:45 ` Peter Zijlstra
2017-11-16 9:12 ` Quan Xu
2017-11-16 9:45 ` Daniel Lezcano
2017-11-20 7:05 ` Quan Xu
2017-11-20 7:05 ` Quan Xu
2017-11-20 18:01 ` Daniel Lezcano
2017-11-20 18:01 ` Daniel Lezcano
2017-11-20 18:01 ` Daniel Lezcano
2017-11-20 7:05 ` Quan Xu
2017-11-16 9:45 ` Daniel Lezcano
2017-11-16 9:45 ` Daniel Lezcano
2017-11-16 9:53 ` Thomas Gleixner
2017-11-16 9:53 ` Thomas Gleixner
2017-11-17 11:23 ` Quan Xu
2017-11-17 11:23 ` Quan Xu
2017-11-17 11:23 ` Quan Xu
2017-11-17 11:36 ` Thomas Gleixner
2017-11-17 11:36 ` Thomas Gleixner
2017-11-17 11:36 ` Thomas Gleixner
2017-11-17 11:36 ` Thomas Gleixner
2017-11-17 12:21 ` Quan Xu
2017-11-17 12:21 ` Quan Xu
2017-11-17 12:21 ` Quan Xu
2017-11-17 12:21 ` Quan Xu
2017-11-16 9:53 ` Thomas Gleixner
2017-11-16 9:12 ` Quan Xu
2017-11-16 9:12 ` Quan Xu
2017-11-15 12:11 ` Peter Zijlstra
2017-11-13 10:06 ` Quan Xu
2017-11-15 21:31 ` [PATCH RFC v3 0/6] x86/idle: add halt poll support Konrad Rzeszutek Wilk
2017-11-15 21:31 ` Konrad Rzeszutek Wilk [this message]
2017-11-15 21:31 ` [Xen-devel] " Konrad Rzeszutek Wilk
2017-11-20 7:18 ` Quan Xu
2017-11-20 7:18 ` Quan Xu
2017-11-20 7:18 ` Quan Xu
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